Merchant Ship Naval Augmentation Program (MSNAP) features and equipment are designed to enable specific merchant-type ships to augment and, when needed, act as CLF vessels during a crisis or conflict. These ships are CINC-allocated assets in service with MSC or maintained in the RRF to support Navy ships. Ships modified with MSNAP systems will be activated and deployed to US or overseas ports for loadout. They will resupply fleet ships with ordnance, other dry stores, or POL. The major MSNAP systems are the Underway Replenishment Consolidation (UNREP CONSOL) System, Vertical Replenishment decks (VERTREP), Modular Cargo Delivery System (MCDS), Modular Fuel Delivery System (MFDS), and Astern Refueling Rigs.

In 2002 some MSNAP elements were re-aggregated under the designation Sealift Enhancement Feature (SEF). The SEF upgrades consist of the Underway Replenishment Consolidation (UNREPCONSOL) system, the Modular Cargo Delivery Station (MCDS) system, the Modular Fuel Delivery System (MFDS), and the Offshore Petroleum Discharge System (OPDS). SEF thus lacks the VERTREP and Astern Refueling Rig elements previously present in MSNAP, while adding the OPDS. MSNAP is focused on the underway replenishment of US Navy warships, while SEP is a sealift activity in support of Marine Corps and Army power projection ashore.

Vertical Replenishment [VERTREP] is provided by adding an elevated deck at the stern of the ship. This installation has been done on three Consol and six MCDS ships. The deck is approved for daylight hours, hover-only operations. The helicopters are from ships being resupplied. Helicopters up to the size of a CH-53E can use this system. Strike-up and pre-stage from the ship's hold to the VERTREP deck capability is provided.

The Modular Cargo Delivery System [MCDS] enables dry cargo merchant ships to perform limited Standard Tensioned Replenishment Alongside Method (STREAM) UNREP operations with all naval ships equipped with a dry cargo UNREP receiving station. The MCDS is a self-contained Navy Standard dry cargo STREAM station. Modifications include those similar to the consolidation system for cargo handling cargo stowage. Additionally, two MCDS units are installed over hatches, one forward and one aft of the ships superstructure. Installations have been made on seven RRF ships.

The Modular Fuel Delivery System [MFDS] enables MSC, RRF, or commercial US flag tankers to deliver POL to Navy oilers and other ships via a modularized, alongside delivery system. The tanker modification provides two delivery stations plus one dry cargo, receive-only station. MFDS has been installed on two tankers that operate with MSC's peacetime fleet.

Astern refueling rigs permit tankers to provide limited POL transfer underway to US and allied combatant ships. Selected tankers are being modified for this system, which involves installation of deck mounting pads, piping modifications, manifolds, valves, and electrical power leads to connect the normal discharge system to a manifold at the stern refueling station. This will permit the contingency installation of a reel-mounted astern refueling rig.

Navy reservists comprise Cargo Afloat Rig Teams [CARTs] that assist the ships' crews during underway replenishments and are usually assigned to ships that have been outfitted with a Modular Cargo Delivery System. The MCDS is a 46 1/2-foot tower placed on the main deck of a ship that allows a cable to run between the supplying ship and the customer ship. When the cable is connected, the supply ship can transfer cargo to the customer ship across the connecting cable. Ships that have the MCDS on board become doubly useful to Military Sealift Command because they can function both as point-to-point cargo carriers and as fleet auxiliary ships that take supplies directly to war ships, allowing the combatant fleet to remain on station for longer periods.

As of 2005 there were seven CARTs assigned to RRF ships with MCDSs on board and two units assigned to work aboard MSC ammunition ships USNS Santa Barbara and USNS Kilauea. Each unit receives its specialized training at the MSC Underway Replenishment Training Center at Naval Weapons Station Earle, NJ, aboard ships during annual exercises and at reserve centers with material provided by MSC.

Military Sealift Command's NFAF UNREP DET Center at Naval Weapon Station (NWS) Earle has been extensively involved with the training of crews (both civilian and military) for the Merchant Ship Naval Augmentation Program (MSNAP) since 1996. An average of 1100 students receive training annually whether on site or via exportable training on board ships or at Naval Reserve Centers. Most of the courses involve extensive hands-on training. Safety is paramount and personnel are taught by the book and correct ordnance handling procedures and administration. The Instructors all have well-documented experience in their areas of expertise. The program has a well-earned reputation for the quality and depth of the training provided.

The training center has the infrastructure in place to rapidly mobilize to provide emergent training requirements for MSC NFAF MSNAP programs as proven by deployments to San Diego, Indian Island, Alameda, Guam, Saipan, Pearl Harbor and Diego Garcia. During Operation IRAQI FREEDOM, the training center provided crucial and effective rapid support to fulfill the demanding training schedule requirements enabling Cargo Afloat Rig Teams (CARTs) to man-up and deploy to four activated ships. Training was provided in Land based facilities as well as shipboard in CONUS and Overseas.

The MSNAP Engineering Department is primarily responsible for ensuring the Modular Cargo Delivery System (MCDS) Modules aboard the MSNAP CAPE vessels are in an A1 ready condition in preparation for contingencies or war. To make this happen, department team members regularly conduct System Operability Tests (SOTs) on the modules as well as perform necessary maintenance and repairs on the underway replenishment equipment. When an MCDS vessel is activated, department personnel standby as a "fly-away" team ready to assist onboard CART Engineers with MCDS maintenance and repairs. A secondary role of the department includes providing technical support to the MSNAP Program in areas of MHE/OHE maintenance, facility management, and general engineering services.